Cochlear implant surgery can be an immense auditory, linguistic and developmental benefit to patients with severe hearing deficiencies caused by the loss of hair cell transduction within the cochlea. The surgical procedure is potentially complicated by difficulties with implanting electrode array insertion and serious complications may occur.
One particularly challenging step is the actual insertion of the implant into the cochlea. After accessing the scala tympani (via direct round window insertion, or drilling open a cochleostomy to gain access to the cochlea), an electrode array is inserted into the scala tympani of the cochlea. Several designs of cochlear implant arrays have relied on stylet-based insertion techniques.
Over the past 6 years, the Cochlear Corporation Freedom and C512 arrays have used a stylet-based strategy. In particular, a stylet is used to hold the implant straight while it is inserted to a desired depth into the cochlea. The array is advanced over the stylet, which is held in a fixed position. The implant naturally curves to follow the cochlea. The stylet is then withdrawn. If the stylet and implant are advanced too far into the cochlea, the resulting contact forces can damage the cochlea. There is also research to replace the stylet with a sheath around the electrode array to hold it straight while the implant is inserted down the scala tympani of the cochlea. One example of such a sheath is the Modiolar Research Array (R. Briggs et al., “Development and evaluation of the modular research array—multi-centre collaborative study in human temporal bones”, Cochlear Implants Int. 2011 Aug. 12 (3) pp. 129-139, PMCID: PMC3159433).
Several approaches to providing guidance or assistance in avoiding damage to the cochlea during implant insertion have been reported recently. In particular, Schurzig, Labadie, and Webster report a system that combines an “active cannula” robot with delicate force sensing capabilities to sense contact between the implant and the cochlea, using a force sensor incorporated into the robotic mechanism that advances the implant into the cochlea. D. Schurzig, R. F. Labadie, and R. J. Webster, “A force sensing robot for cochlear electrode implantation”, in IEEE International Conference on Robotics and Automation, 2010, pp. 3674-3679. Rau et al. have also proposed a robotic cochlear insertion device and have reported phantom studies of insertion forces using a load cell attached to the insertion mechanism.
Zhang, Simaan, et al. have developed an actively deforming, steerable, cochlear implant that curves to follow the cochlea during insertion. See e.g., J. Zhang, W. Wei, S. Manolidis, J. T. Roland, Jr., and N. Simaan, “Path planning and workspace determination for robot-assisted insertion of steerable electrode arrays for cochlear implant surgery”, Med Image Comput Comput Assist Interv, vol. 11—Pt 2, pp. 692-700, 2008; J. Zhang, K. Xu, N. Simaan, and S. Manolidis, “A pilot study of robot-assisted cochlear implant surgery using steerable electrode arrays”, Med Image Comput Comput Assist Interv, vol. 9—Pt 1, pp. 33-40, 2006; J. Zhang, W. Wei, J. Ding, J. T. Roland, S. Manolidis, and N. Simaan, “Inroads Toward Robot-Assisted Cochlear Implant Surgery Using Steerable Electrode Arrays”, Otology and Neurotology, p. in Press; Published ahead of print, 2010 10.1097/MAO.Ob013e3181e7117e. They report experiments using a load cell mounted on their robotic manipulation device. Some limitations of these systems include reliance on a fairly large and cumbersome robotic insertion tool and the necessity to implement an extremely delicate force sensing mechanism. In the case of the reported systems, the difficulty is exacerbated by the moving mass of the mechanism distal to the force sensor and possible friction forces.
Other authors have proposed robotic devices to assist in drilling the skull to gain access to the cochlea for implant insertion. These systems do not address the problem of inserting an implant without damage to the cochlea. See, e.g., C. J. Coulson, R. P. Taylor, A. P. Reid, M. V. Griffiths, D. W. Proops, and P. N. Brett, “An autonomous surgical robot for drilling a cochleostomy: preliminary porcine trial”, Clin Otolaryngol, vol. 33-4, pp. 343-7, August 2008; and O. Majdani, D. Schurzig, A. Hussong, T. Rau, J. Wittkopf, T. Lenarz, and R. F. Labadie, “Force measurement of insertion of cochlear implant electrode arrays in vitro: comparison of surgeon to automated insertion tool”, Acta Oto-Laryngologica, vol. 130-1, pp. 31-36, January 2010.
Skilled otologic surgeons have the manual dexterity and steadiness to insert implants without damage to the cochlea. What they lack is feedback to know when the implant or stylet has been introduced too far into the cochlea. See, e.g., C. J. Coulson, A. P. Reid, D. W. Proops, and P. N. Brett, “ENT challenges at the small scale”, Int J Med Robot, vol. 3-2, pp. 91-6, June 2007.
Accordingly, there is a need in the art for a system that allows a surgeon information regarding the location of the implant with respect to the cochlea walls.